Fluid jets have been used to cut food, paper and other products for years. The advantages are numerous: there are no blades that need to be sharpened or replaced, no dust is created, and cuts can be quick and clean. The cutting is done with a thin, high pressure, high velocity stream of water or other fluid. Pressurized water is ejected from a very small orifice to create the jet. When the jet touches the product, a thin slice is removed without any appreciable water being absorbed into the product.
Specific manipulation of the flow of fluid emanating from the water jet accurately cuts shapes in the products. Many of the shapes desired require precise high speed interruption of the water jet. The greater the detail of the desired shape of the product, the faster the interruption of the jet must be in order to attain such detail. Also, a higher rate of interruption results in less processing time.
Various ways have been taught to interrupt the water jet at high speeds. One such method of interruption is that of inserting an object between the source of the high speed water jet and the product. A linear actuator pressurized by air that forces a plunger pin into the path of the water jet is a generally known tool for performing this method. A spring provides a retracting force for the plunger pin. Existing plunger pin devices are capable of reaching closure times of 50-90 ms and thereby limit the speed at which products may be cut by the water jet.
U.S. Pat. No. 4,693,153 (Wainwright et al.) discloses another water jet interruption technique. When interruption of the object cutting jet is desired, a second high pressure fluid is directed at the object cutting jet so as to disperse the latter and impair its object cutting properties. The device that controls the second fluid flow is similar to the plunger pin device. A solenoid device within the jet obstructer device controls the fluid flow from the jet obstructer device. An energized solenoid closes a plunger mechanism that is normally held in an open position by a spring. In the open position the mechanism provides high pressure fluid to interrupt the object cutting water jet. Similar to the plunger pin device, this device also lacks the high speed interruption capabilities necessary for cutting products as rapidly as may be desired.
International application number WO93/10950 discloses a valve for controlling a constantly running liquid cutting jet. A pneumatically powered rotary cylinder 2 is attached to one end of and elongate plate 1 to rotate the opposite end of the plate in and out of the path of flow of the liquid cutting jet. However, the opening and closing times for this rotary plate are only slightly better than that of existing plunger pin devices. Also, the cutting jet strikes one position on the plate resulting in frequent replacement of the plate.
The prior art described above fails to address the issue of efficient removal of deflected cutting fluid for avoiding absorption into the product. Also the issue of high temperature caused by high speed operation is not addressed. Consistent high temperatures will cause premature failure of the valve device.
The devices currently in use, as exemplified by those described above, do not effectively and efficiently solve the problem of cutting precise shapes at high speeds that require a high frequency of water jet interruption. Accordingly, the present invention was developed, and provides significant advantages over previous devices or methods to cut shapes with fluid jets.